Moscow would face more EU sanctions if pro-Russia separatists attack the Ukrainian port of Mariupol, potentially opening a corridor to the south, including the annexed Crimean Peninsula, French Foreign Minister Laurent Fabius said on Wednesday.
Kiev fears Mariupol, with its 500,000 people, could be the next major rebel target after separatists took the strategic railroad town of Debaltseve, its Foreign Minister Pavlo Klimkin said after cease-fire talks in Paris two weeks ago.
"The problem today is particularly around Mariupol. We've told the Russians clearly that if there was a separatist attack in the direction of Mariupol things would be drastically altered, including in terms of sanctions," Fabius said.
"At a European level the question of sanctions would be asked again," he told France Info radio, having hosted Tuesday's meeting where his Russian, Ukrainian and German counterparts all renewed calls for the cease-fire to be respected.
EU leaders had agreed not to increase or reduce sanctions after German Chancellor Angela Merkel and French President Francois Hollande helped broker a cease-fire deal on Feb. 12.
However, following several breaches of the cease-fire, European Council President Donald Tusk said on Feb. 20 leaders were discussing possible further sanctions to penalize Russia.
A French diplomatic source, however, played down the prospect of more sanctions, saying that it was not an issue Paris supported for now as it would send the wrong message.
"You can't seriously discuss implementing the [Minsk] agreements and in parallel discuss sanctions. We are not entering this debate," the source said.
Rebel commander Eduard Basurin said on Tuesday that the rebels still aimed to gain control of the entire territory of east Ukraine's two rebellious provinces, including Mariupol, but would seek this through "negotiations with the Ukrainian side."
Klimkin told reporters in Paris late on Tuesday, "Mariupol is critical. Any kind of attack on Mariupol would change things ... Debaltseve was a game changer because it disrupted the spirit of the Minsk accords."
"Any further attacks would trigger a counter attack."
Basurin also denied Kiev's assertions that there were serious clashes in villages near Mariupol, saying there had been provocations from the Ukrainian side but no major incidents.